Rig Site Tips

Slow Circulation Rate (SCR)

The slow rates are taken for at least two values. The slow rates are recorded:

- When changing the drilling bit

- When changing the BHA

- When any mud property is changed significantly such as the mud weight

- When changing any mud pump component like liners.

- If no change was carried during operations, the slow circulation rates are taken every night or day shift.
- Reading must be taken from the choke panel not from the rig screen.

Fig 01- Choke Panel

Flow Check

The flow check is performed to guarantee that there is no formation fluids influx which can affect the operations. The flow check is performed for many reasons:

- When noticing drilling breaks, which is a sign of drilling through a high porosity formation.

- When drilling through an expected top of a reservoir

- When noting an unexplained or abnormal increase in active mud pit level

- When recording an increase or decrease in mud pump flow rate (strokes per minutes – SPM)

The flow check is performed as follows:

- The drilling has to be ceased, and the drill string has to be pulled away from the bottom at least for one or two meters

- Stop the mud pumps

- Start to monitor the flow return in the flow line. If any flow of mud is noticed, the well has to be shut in and the casing and pipe pressure has to be recorded to proceed to the well control situation.

Drill Off Test

The drill off test permits to determine the value of weight on bit (WOB) and revolution per minute (RPM) in order to get the optimized rate of penetration (ROP).

This test is performed without any special preparation, and has to be performed when changing the drill bit.

The test is divided into two parts:

- Identifying the optimum weight on bit

- Identifying the optimum revolution per minute

The optimum weight on bit is identified as follows:

- Apply the maximum weight on bit which is designed for the chosen drill bit according to its technical data.

- Maintain the RPM at a stable level

- Record the needed time to get a pre-defined decrease in weight on bit (ex: 2 Tons- from 22 T to 20T, from 20T to 18T, from 18T to 16 T…….)

- Stop the test when you notice a significant increase in time.

- The optimum weight on bit is the value which has the shortest time

The optimum RPM is identified as follows:

- Make a mark on the drill pipe each 0.5 meter

- Apply the optimum weight on bit

- Record the time to drill 0.5m using different values of RPM

- The optimum RPM is the value which corresponds to the shortest recorded time

Shoe Bond Test (SBT)

The shoe bond test is performed in order to evaluate the integrity of cement around the shoe. The shoe bond test is performed by the cementing unit; the testing fluid (drilling mud) can be pumped through the choke manifold (through the annulus) or through the drill pipe using a circulating head.

This test is obligatory in some cases:

- A stuck casing string which is cemented above the planned setting depth

- A bad cementing job when the quality of the pumped cement was a doubtful issue

- Losses while cementing the casing string

- Not getting the pressure bumps

Some steps have to be followed before starting the test:

- Drilling one meter through the new formation bellow the shoe

- Pull out the drill string above the casing shoe by few meters

- Make a circulation in order to clean the hole and homogenize the drilling fluids ( the mud weight of the drilling fluid flowing out of the hole has to be the same as the mud weight of the drilling fluid flowing into the well)

- The cement unit has to be tested, also the lines which lead to choke manifold and from the choke manifold to the choke line.

- The safety valve has to be set at top of the drill string in closed position

When the well is cleaned which can be confirmed on the shale shakers, the test can be started as follows:

- Isolate the well by closing the BOP ( ex: pipe rams)

- Start pumping using the cementing unit at constant flow rate

- Use the minimum possible flow rate which can be pumped by the cementing unit( 0.25 to 0.5 barrel per minute)

- Record the trend of pressure

The test is stopped when reaching the desired testing pressure or when a significant pressure decrease in the trend is recorded.

After stopping the test:

- Bleed off the pressure into the cement unit tanks

- Record the pumped fluid volume

- Open the well

- Check that everything is ready to resume drilling

The pressure of test is calculated as follows:

Ptest: The test pressure (Psi)

MWe: Equivalent mud weight defined into the drilling program (ppg)

MWwell: Mud weight which exists into the well (ppg)

TVD: total vertical depth (Casing shoe depth) (ft)

Running a Bottom Hole Assembly (BHA):

Running a new BHA in the well has to be well planned in order to avoid any non-productive time (NPT). The preparation involves many actions:

- Checking the availability of all the equipment and components which will be used in the next run

- Making sure that the stabilizers are in good state and their gauges are adequate to be run

- Checking the threads and that all the components are adapted to be screwed together

- Making sure that the number of operating hours of the drilling jar will not exceed the maximum operating hours while drilling the next section.

The drilling bit has also to be prepared:

- Check the gauge of the drilling bit

- Check the nozzles that they are well set and they are not plugged

- Check the threads of the drilling bit

Before running the BHA in the hole, some precautions have to be carried out:

- Close the well when making up the drilling bit to avoid losing anything in the well which can lead to fishing operations

- Make sure that the safety valve is set in good position

- Measure the length of the make-up tongs

- Check the make-up torque before screwing the bit

Preparing The Casing String:

The casing has to be prepared before running in the hole and this has to be performed during drilling operations.

Some steps have to be performed in appropriate way in order to avoid any non-productive time. These steps can be summarized as follows:

- When the joints arrive on site, count them to get the exact number of joints to do not be confused in case of casing string stuck.

- The joints have to be cleaned and drifted

- Make sure that the drift is the one which is appropriate for the casing

- After cleaning the threads check them visually, if any doubt about the thread remove that joint

- Measure the threads length to get your string length on the casing tally

- Mark the joints which are considered '' out of run '' then remove them from the total joints

- Be sure that the joints have the same characteristics especially the threads

- If some joints which are used in the shoe track and they do not have the same threads type, cross over joints have to be used to make up the joints together.

- Make sure that casing shoe and the landing collar are on site and they have the same threads type like the casing joints, if not cross over joints have to be ordered.

- Check the valve into the landing collar

- Check if the casing hanger is on site and it is suitable for the casing spool

- Check if there is enough centralizers and stop collars for the next run

- Try to use the longest joints for the shoe track to get excess of cement volume in case when the pressure bumps are not recorded

- If any doubt about the running, try to get pup joints for spacing out.

Fig 02- Prepared Casing On Rig Site